Download file of any type in Asp.Net MVC using FileResult?

You can just specify the generic octet-stream MIME type:

public FileResult Download()
{
    byte[] fileBytes = System.IO.File.ReadAllBytes(@"c:\folder\myfile.ext");
    string fileName = "myfile.ext";
    return File(fileBytes, System.Net.Mime.MediaTypeNames.Application.Octet, fileName);
}

The MVC framework supports this natively. The System.Web.MVC.Controller.File controller provides methods to return a file by name/stream/array.

For example using a virtual path to the file you could do the following.

return File(virtualFilePath, System.Net.Mime.MediaTypeNames.Application.Octet,  Path.GetFileName(virtualFilePath));